The present invention relates to a disk device and, in particular, to a disk device that has a servo mechanism, eliminates improper selection of a head to improve reliability in the recording and reproducing of information, and thus can be realized without decreasing format efficiency thereby.
In a conventional disk device, a servo mechanism for positioning a head is an essential technology.
For example, a magnetic disk device is provided with a mechanism part having a voice coil motor (hereinafter referred to as VCM) for driving and positioning a magnetic head which records or reproduces information on or from a disk storing medium on which information is to be recorded and a drive circuit for driving the mechanism part. Then, in order to correctly and at high speed control medium information recorded at a high recording density, a sector servo mode in which the positioning of the foregoing magnetic head is performed based on servo information recorded on the top of a sector of a data recording surface or a servo mode based thereon is generally utilized.
Further, a technology that increases a storage capacity by increasing format efficiency has been proposed for the magnetic disk device strongly required to reduce its size and to increase its capacity. For example, in Japanese Patent Laid-open No. 1993(H5)-174498, entitled “Sector Architecture for Disk File of Fixed Block Mode” is disclosed a technique for deleting an ID region provided to identify a data sector, that is, an “ID-less mode” technique.
A servo information recording region generally includes an automatic gain control (AGC) region, a servo address mark (SAM) region, a servo sector address (SSA) region, a gray code track region, and a burst region.
Then, the magnetic head generates in the AGC region a reference signal of servo information in which detection sensitivity and detection frequency are adjusted, detects the position of the servo information recording region in the SAM region, detects a servo sector number in the SSA region, detects a track position in the gray code track region, and detects the position error information between the tracks in the burst region. In the above-mentioned ID-less mode, the data sector does not include an ID part in which a data sector address (DSA) is stored and thus determines the DSA by the use of the SSA.
In a format mode using the foregoing ID-less mode in the related art, the data sector is detected by identifying a servo sector address (SSA) stored in a servo sector and then converting the SSA into a data sector address (DSA) by the use of a conversion table or the like.
However, this detection of the data sector is to identify the data sector on a track where a head is to be positioned. Thus, in a case where a track different from a desired track is selected by the failure or disoperation of a head switching circuit in a disk device having a plurality of recording surfaces and a plurality of heads, there is a possibility that the incorrect selection will not be detected but the data sector will be misidentified to record or reproduce the data by the use of the incorrect data sector thereby to destroy user's data or to transfer the incorrect data to a host computer.
For this reason, it is required to detect a track where the head is actually positioned.
For the purpose of detecting this incorrect selection of the head, for example, in Japanese Patent Laid-open No. 1998(H10)-269729 titled “Disk Device” is proposed a technique in which there are provided a data region where data is recorded on or reproduced from the recording surface of a disk, a servo region where servo information used for controlling the positioning of a head over the recording surface of the disk is recorded, and a servo check region (SCF 30 in FIG. 2) where information used for determining an error of positioning a head (error of selecting a head) is recorded; and in which servo check information (head number, cylinder number or the like) stored in the servo check region is reproduced to identify a track over which a head is actually positioned, whereby when data is recorded or reproduced, incorrect selection of the track is prevented thereby to protect user's data.
However, this technique in the related art presents a problem that it can prevent the user's data from being destroyed by the incorrect selection of the head but it needs a new region for the servo check information thereby to inevitably decrease a data region, that is, to incur a decrease in format efficiency.
The present invention has been made to solve the problem of the foregoing technique in the related art. It is the object of the present invention to provide a disk device in which heads are positioned by a servo mechanism and can prevent data from being destroyed by incorrect selection of a head to improve reliability in the recording or reproducing of information and can be realized without decreasing format efficiency thereby.